Field
Exemplary embodiments of the present invention relate to a display substrate and a method of fabricating the same. More particularly, exemplary embodiments of the present invention relate to a display substrate including a direct contact part (D-CNT) using an etch stopper scheme and reducing the number of photo masks used in the fabrication of the display substrate for a liquid crystal display device in a Plane Line Switching (PLS) mode.
Discussion of the Background
A liquid crystal display device displays an image by adjusting light transmittance of liquid crystals through an electric field. The liquid crystal display device may include a liquid crystal panel, in which liquid crystal cells are arranged in a matrix form, and a driving circuit for driving liquid crystals.
The liquid crystal panel may include a display substrate forming a thin film transistor array, a color filter substrate forming a color filter array, and liquid crystals interposed between the two substrates.
In the liquid crystal panel, the liquid crystal cells may be arranged in regions where gate lines and data lines cross. Each of the liquid crystal cells may form a pixel electrode and a common electrode, to which an image data signal and a common voltage is applied, respectively. Further, a thin film transistor connected to the gate line, the data line, and the pixel electrode may be formed in the liquid crystal cells, so that when a scan signal is supplied to the gate line, the data line supplies the image data signal to the pixel electrode in order to display an image.
The liquid crystal display device may be classified into a vertical field mode liquid crystal display device and a horizontal field mode liquid crystal display device depending on a direction of the electric field.
The liquid crystal display device has been developed because a wide viewing angle for the vertical field mode liquid crystal display may be deteriorated. Particularly, research has been conducted for reducing manufacturing cost of a Plane to Line Switching (PLS) mode liquid crystal display device which is a type of horizontal field mode liquid crystal display device.
An inverted staggered structure of a bottom gate may be used for fabrication of the display substrate, since its manufacturing process may be relatively simple, and does not require a separate light blocking layer. A thin film transistor having the inverted staggered structure may be classified into a Back Channel Etched (BCE) scheme thin film transistor, which may be used for simplifying a manufacturing process, and an Etch Stopper (ES) scheme thin film transistor, which may be used for improving a characteristic of the thin film transistor, depending on a manufacturing process of forming a channel.
The BCE scheme may be used to etch an ohmic contact layer after forming a data pattern in order to decrease the number of masks used and continuously fabricate a gate insulating layer, a semiconductor layer, and the ohmic layer within the same chamber. However, in order to completely remove the ohmic contact layer of a channel part, over-etching may be required, which may require forming a thick semiconductor layer to secure a margin. Accordingly, an increase in processing time, a leakage current, and a serial contact resistance of the thin film transistor may occur, and a decrease in electron mobility of the liquid crystal device may also occur.
The ES scheme may form a thin semiconductor layer, but may require patterning an etch stopper, which may require an additional mask process.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the inventive concept, and, therefore, it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.